Previous research indicates that under prolonged low environmental temperature (cold-stress), the photoreceptors of the retina of the goldfish beome dysfunctional and appear to undergo degeneration. These factors appeared to be only partially reversed on removal of the precipitating influence. The proposed research seeks to determine potential causal mechanisms, generality across species, and possible involvement of cells of the pigment epithelium as well as provide additional description of factors influencing this new phenomenon. Electrophysiology, structure and ultra-structure, indices of cellular function and integrity, will be the dependent variables in a series of experiments designed to; study the influence of altered metabolic drain on photoreceptors on cold-stress effects by manipulating environmental light level, provide comparative data across species, mimic the effects of cold-stress by inducing hormonal imbalance as a result of pinealectomy, determine the decay function of effects on photoreceptors with stressing temperature for comparison to similar functions for basic biochemical and metabolic mechanisms and investigate pigment epithelium dysfunction as a potential causal factor to which photoreceptor effects are secondary. The use of electron microscopy in these studies will allow assessment of differential cold-stress effects on rods and cones suggested by electrophysiology in earlier work. In addition, description of the influence of cold-stress on photomechanical responses of retinal structures of several species employed will be a factor in these investigations.